1. Field of the Invention
The present invention relates to novel optical recording materials suitable for, mainly, laser recording and reading, a method for preparing the same and optical cards having the same.
2. Description of the Prior Art
With recent remarkable progress of laser-related technologies as well as development of digitalization of information, various types of optical recording materials have been proposed.
As representative digital recording material, optical disks can be mentioned. Separately, for easy handling there have been proposed optical card materials made from high capacity flexible digital recording materials like optical disks (for example, U.S. Pat. Nos. 4,278,756; 4,463,089; and 4,692,402). Also, as the recording material in which higher capacity information can be recorded more compactly compared with optical disks there have been proposed optical tapes and further, optical floppy disk systems which are less expensive than optical disk systems. In accordance with these proposed systems various optical recording materials have been developed. When these optical recording materials are made more compact in shape or form for carrying, they are expected be exposed to very sever conditions affected by, for example, sunlight, open air temperatures, high temperatures within automobiles in summertime and high humidities due to body temperature and perspiration. However, various properties required for them such as recording sensitivity, storage stability, recording density and error bit ratio are still not sufficient. In particular, in the applications for optical cards, optical tapes and optical floppy disks which require flexibility, novel recording materials having storage stability and reliability, which can be produced by a continuous coating step suitable for mass production at low cost are eagerly desired.